DC-AC power inverter controlled analogically with zero hysteresis

This paper presents the design and experimental validation of a DC-AC power inverter, controlled analogically with zero hysteresis. A control circuit was built using analog electronics components, and optocoupler devices are used to couple the control module with the power stage. The design of DC-AC inverter with electronics circuit and implementation are shown in detail.  Experimental results show the effectiveness of control technique and implementation, leading to a robust system concerning load disturbances. The developed inverter offers the possibility of generating regulated output voltages of different signal types, both DC and AC, variable in frequency and in amplitude, useful for feeding a load with various AC signals

Unsteady state series CSTR modeling of removal of ammonia nitrogen from domestic wastewater treated in a vertical flow constructed wetland

This work shows simulation results for subsurface vertical flow constructed wetland (VFCW) using a series CSTR model. The VFCW considered received the outflow from a domestic wastewater treatment plant. In addition, it was planted with Cyperus sp. and filter media was unsaturated. The model was based on an unsteady state mass balance for ammonia, nitrites, and nitrates, using one to three series CSTRs. Nitrogen transformation mechanisms considered were ammonification, nitrification, plant uptake and denitrification. The following effects were evaluated: the number of reacting CSTRs from one to three; the occurrence of the reaction in second and third CSTRs for the case that three CSTRs hold; the use of either equal or different values of reaction rate parameters between CSTRs; and the discretization of the reaction rate parameters. The inflow and outflow measurements of ammonium, nitrites, and nitrates were used for model calibration. The estimated parameters included the reaction rate coefficients and reactor water volume. The coefficient of determination (R2) evidenced a satisfactory capability of simulating outlet pollutant concentrations. Two and three reacting CSTRs achieved similar R2 value (0.54-0.55), whereas one reacting CSTR achieved an R2 of 0.39, and three CSTRs with reaction only in the first tank achieved an R2 of 0.42. Discretization of the nitrification rate for the case of two reacting CSTRs led to an R2 of 0.94. The parameter sensitivity analysis revealed a significant effect of model parameters on the R2 value

Fractal representation of the power demand based on topological properties of julia sets

In a power system, the load demand considers two components such as the real power (P) because of resistive elements, and the reactive power (Q) because inductive or capacitive elements. This paper presents a graphical representation of the electric power demand based on the topological properties of the Julia Sets, with the purpose of observing the different graphic patterns and relationship with the hourly load consumptions. An algorithm that iterates complex numbers related to power is used to represent each fractal diagram of the load demand. The results show some representative patterns related to each value of the power consumption and similar behaviour in the fractal diagrams, which allows to understand consumption behaviours from the different hours of the day. This study allows to make a relation among the different consumptions of the day to create relationships that lead to the prediction of different behaviour patterns of the curves

Optimal parameters of inverter-based microgrid to improve transient response

The inertia issues in a microgrid can be improved by modifying the inverter control strategies to represent a virtual inertia simulation. This method employs the droop control strategy commonly used to share the power of a load among different power sources in the microgrid. This paper utilizes a modified droop control that represents this virtual inertia and applies an optimization algorithm to determine the optimal parameters and improve transient response. The results show better control when different variations are presented in the loads, leading the microgrid to have a better control of the operation. The optimization method applied in this research allows improvement to the transient response, thus avoiding unnecessary blackouts in the microgrid

Performance evaluation of a DC-AC inverter controlled with ZAD-FPIC

Introduction− Power converters are used in mi-crogrids to transfer power to the load with a regulated voltage. However, the DC-AC converters present distor-tions in the waveform that can be improved with the help of real-time controllers.Objective−Evaluate the response in alternating cur-rent of the buck converter controlled with the ZAD-FPIC technique.Methodology−Based on the differential equations that describe the buck power converter, the ZAD and FPIC controllers are designed. Afterwards, simulations of the complete controlled system are made using Simulink of MATLAB. Then, the system is implemented experi-mentally and the controller is executed in real-time with the help of a DS1104 from dSPACE. In the end, several tests are carried out to check the effectiveness of the controller.Results− The results show that the controller allows good stability against different variations in the system and in the load.Conclusions−The ZAD-FPIC technique controls the variable and tracks changes in the waveform, magni-tude, and frequency of the reference signal. The control-ler presents good stability to different tests, tracking the reference signal after each event.Introducción− Los convertidores de potencia son utili-zados en las micro redes para transferir la potencia a la carga con una tensión regulada. Sin embargo, los conver-tidores DC-AC presentan distorsiones en la forma de onda que pueden ser mejoradas con la ayuda de controladores en tiempo real.Objetivo− Evaluar la respuesta en corriente alterna del convertidor buck controlado con la técnica ZAD-FPIC.Metodología− Se parte de las ecuaciones diferenciales que describen el convertidor de potencia buck, luego se diseñan los controladores ZAD y FPIC, se hacen simu-laciones del sistema completo controlado en Simulink de Matlab, se implementa el sistema de forma experimental y el controlador se ejecuta en tiempo real con la ayuda de una DS1104 de la empresa dSPACE, al final se realizan varias pruebas para comprobar la efectividad del controlador.Resultados− Los resultados muestran que el controlador permite que una buena estabilidad contra diversas varia-ciones en el sistema y en la carga.Conclusiones− La técnica ZAD-FPIC controla la varia-ble y realiza seguimiento ante cambios en la forma de onda, magnitud y frecuencia de la señal de referencia. El controlador presenta buena estabilidad ante diferentes pruebas, siguiendo la señal de referencia después de cada event

Buck converter controlled with ZAD and FPIC for DC-DC signal regulation

This paper presents the performance of a fixed-point induction control (FPIC) technique working in conjunction with the non-linear control technique called zero average dynamics (ZAD) to control chaos in a buck converter. The control technique consists of a sliding surface in which the error tends to zero at each sampling period. A switch is controlled by using centered pulse width modulation (CPWM) control signal. The converter controlled with ZAD-FPIC has been simulated in Matlab and implemented using rapid control prototyping (RCP) in a DSP to make comparisons between simulation and experimental tests. To perform this comparison, some variations in the control parameter and the voltage reference are made in order to evaluate the performance of the system. Results are obtained with errors lower than 1 % which demonstrates the good performance of the control techniques

Reactive power sharing in microgrid using virtual voltage

The traditional droop control strategy has been applied previously in microgrids (MGs) to share accurately the active power. However, in some cases the result obtained when sharing reactive power is not the best, because of the parameters related to the distances from distributed generators (DGs) to the loads and the power variations. Therefore, this paper proposes a reactive power control strategy for a low voltage MG, where the unequal impedance related to the distances between generators and loads requires adjustments to work with the conventional frequency and voltage droop methods. Thus, an additional coefficient is calculated from parameters of the network that relate the location of elements. The test is perfomed by simulations in the MATLAB-Simulink software, considering a three-node MG with three DGs and a load that can change power at different periods of time. The results show that it is possible to improve reactive power sharing between the DGs located in the MG according to the load changes simulated and to improve voltages with this method

Strategies for use, treatment, management and final disposition of wastes in academic laboratories

Laboratory higher education institutions can generate a wide range of wastes,many of which have hazardous characteristics. The uncontrolled accumulation of such wastes also has a significant impact on the environment, safety and health of the academic community. This work formulates strategies that allow the development of integrated solutions to mitigate the latent risk for the community at Institución Universitaria Colegio Mayor de Antioquia,Colombia, and its surroundings. Therefore, it is considered to quantify the generation of waste in the units of analysis of different experimental spacesand evaluate the factors involved in the implementation of strategies for diagnosis, waste recovery, treatment, and final disposition. Based on the diagnosis and characterization of wastes, alternatives are evaluated that help to prevent and, in other cases, mitigate the impacts that they can cause, in order to consolidate a protocol for waste management. Hazardous waste disposition strategies, treatment mechanisms and minimization strategies, such as microchemistry, precipitation recycling, encapsulation and immobilization methods, evaporation as well as solvent recovery, have been implemented

Characterization of excitation source LEDs and sensors without filters for measuring fluorescence in fluorescein and green leaf extract

This paper presents the characterization of excitation source LEDs and sensors without filters for measuring fluorescence in fluorescein and green leaf extract. For this purpose, eight light-emitting diodes (LEDs) were used with the following characteristics: one blue, one green, one red, one infrared, and four violets. The first four LEDs were used as sensors without filters to detect fluorescence induced by the other four violet LEDs in 11 samples of different fluorescein concentrations and in 14 samples of different dilutions of green leaf extract. The results show that infrared LEDs can detect the red emission of green leaf extract and red and infrared LEDs detect the fluorescence of fluorescein in concentrations of up to 1.8 μM. The developed system allows and facilitates teaching optical spectroscopy in basic education without incurring high costs